“Rain will spread quickly northeast across much of Northern Ireland this evening, but is expected to be heaviest across parts of south Down, and especially south-facing slopes of the Mournes,” the weather service said.
A yellow warning for rain has been updated for parts of Wales and southwest England and will now come into effect from midnight Friday until 10am Saturday.
Upto 50mm of rainfall could fall around the hills of southwest Wales and the southern slopes of Dartmoor, the Met Office said, as localised flooding is also expected.
It comes as frosty weather is expected in the northeast of Scotland on Saturday as Met Office meteorologist Aidan McGivern said: “For the start of Saturday, we keep the cold conditions at first across parts of central and eastern Scotland, so there will be a touch of frost in the northeast of Scotland and some snowflakes over the hills and mountains, as the rain bumps into that cold air.”
The fresh weather alerts come after Storm Debi left the UK reeling as it unleashed widespread flooding and devastating winds across many parts of the country this week, particularly in Northern Ireland.
Severe gales caused power cuts across the island of Ireland, with around 100,000 homes and businesses left without electricity.
Gusts of 77mph were recorded in Gwynedd, 74mph at Killowen in Northern Ireland and 68mph on the Isle of Man as the low pressure system moved across the Irish Sea.
Dry with clear spells in the east, perhaps with some early frost and fog in places. Cloud and rain pushing steadily eastwards. Winds strengthening. Mild, particularly in the south.
Cloud and rain spreading north and east throughout the day. Some heavy bursts in places. Sunny spells and showers following from the west. Windy, particularly near coasts.
Sunny spells returning on Sunday with the risk of blustery showers which will continue into Monday. Most places becoming dry on Tuesday. A touch of frost possible in the north.